Here we go again. IMO, unless you have a specific problem you are trying to fix I see no point in arbitrarily running a system cleaner. I believe you are just as likely to cause as many problems as you avoid. If you are trying to perform disk cleanup run the disk cleanup utility.

The best clean up utility is in your control panel under "Programs and Features", just click away. For mech drives, don't forget to defrag after.
Personally, I like the "format.exe" the most. It's the deepest clean there is.

In all seriousness, Joe is correct.
You should be more specific in what you are attempting to "clean".

The original question seems to have been asked by a true newbie. That's when I am VERY careful with any advice.

Recommending CCleaner entails the risk of this person being over-vigilant.
- Removing all entries listed in Startups would leave the system in limited functionality.
- Uninstalling nilly willy things from the Uninstall list only because he/she doesn't recognize them is equally dangerous.

I stated I use both CCleaner and Privacy Mantra. The OP will have to decide for himself whether either will work for him or her. There are many discussions throughout these forums on both file cleaners and registry cleaners. I have stated repeatedly in these discussions that individuals have to be very vigilant in deciding what they remove using such cleaners and if they do not know what something is then it should NOT be removed until investigated.

The default settings in CCleaner does NOT remove all Startup items, but then I disagree about startups. Almost ALL items starting with Windows are NOT necessary. The only items I allow to start with Windows are my AV/AM, Firewall and Touchpad / mouse S/W, nothing else.

CCleaner also does NOT by default uninstall things nilly willy from uninstall. In fact I do not believe there are uninstall items on the CCleaner list at all. Perhaps I'm incorrect but I just looked and did not see any.